This invention relates generally to imaging and, more particularly, to scalable multislice imaging systems.
In at least some imaging systems generally referred as computed tomography (CT) systems, an x-ray source projects a fan-shaped beam which is collimated to lie within an X-Y plane of a Cartesian coordinate system and generally referred to as the “imaging plane”. The x-ray beam passes through the object being imaged, such as a patient. The beam, after being attenuated by the object, impinges upon an array of radiation detectors. The intensity of the attenuated beam radiation received at the detector array is dependent upon the attenuation of the x-ray beam by the object. Each detector element of the array produces a separate electrical signal that is a measurement of the beam attenuation at the detector location. The attenuation measurements from all the detectors are acquired separately to produce a transmission profile.
In known third generation CT systems, the x-ray source and the detector array are rotated with a gantry within the imaging plane and around the object to be imaged so that the angle at which the x-ray beam intersects the object constantly changes. X-ray sources typically include x-ray tubes, which emit the x-ray beam at a focal spot. X-ray detectors typically include a collimator for collimating x-ray beams received at the detector, a scintillator adjacent the collimator, and photodiodes adjacent the scintillator.
In known third generation CT systems, the x-ray source and the detector array are rotated with a gantry within the imaging plane and around the object to be imaged so that the angle at which the x-ray beam intersects the object constantly changes. A group of x-ray attenuation measurements, i.e., projection data, from the detector array at one gantry angle is referred to as a “view”. A “scan” of the object comprises a set of views made at different gantry angles, or view angles, during one revolution of the x-ray source and detector. In an axial scan, the projection data is processed to construct an image that corresponds to a two dimensional slice taken through the object. One method for reconstructing an image from a set of projection data is referred to in the art as the filtered back projection technique. This process converts the attenuation measurements from a scan into integers called “CT numbers” or “Hounsfield units”, which are used to control the brightness of a corresponding pixel on a cathode ray tube display.
To reduce the total scan time, a “helical” scan may be performed. To perform a “helical” scan, the patient is moved while the data for the prescribed number of slices is acquired. Such a system generates a single helix from a one fan beam helical scan. The helix mapped out by the fan beam yields projection data from which images in each prescribed slice may be reconstructed. Total scan time may be further reduced by increasing the number of detector cells in the axis along the patient. An area detector can also be used to collect a volume of data in each rotation.
In a x-ray fluoro system, a flat panel detector can be used to take sequential exposures to track dynamic motion in a patient. This can yield images with high temporal resolution. The images, however, have significant super position artifacts.
In CT fluoroscopic systems (“CT Fluoro”), data collected from a scan may be utilized to generate sequential frames of images. A frame, like a view, corresponds to a two dimensional slice taken through the imaged object. There are no super position artifacts. Particularly, projection data is processed at a frame rate to construct multiple images. With known CT Fluoro systems, the gantry of the CT system is rotated about the area of interest of the patient and sequential images are reconstructed and displayed.
At least one known imaging system utilizes a closed gantry to generate a 3D image of the patient. The 3D images provide object information including depth information. As a result of the closed gantry construction of the CT system, the object is translated through the gantry to generate a 3D image of the object. The translation of the object through the gantry, in addition to being nearly impossible for certain types of objects, causes CT system positioning and use to be difficult.
It would be desirable to provide an multimode imaging system which generates various types of images for the object so that the tradeoffs between devices may be minimized. It also would be desirable to provide such a multimode imaging system which facilitates an open gantry to easy and fast access to the object to be imaged.